Recent Posts

1

DIY / Re: Sentura II Restoration - Tremolo Bug/Roach Replacement Photocell

« Last post by Watson on September 15, 2020, 02:47:18 pm »

Had a few minutes and added a few more changes to the Sentura II schematic.  Just updated it to reflect the 3-prong wiring, updated the input jack wiring and added the mid-boost switch (3PST) in addition to the dual bias pots and probe points.

The 2nd attachment is the "corrected" Sentura II schematic I've been working from. 

If anyone sees a problem in either schematic please call it out.  Thanks in advance.

2

SUNN Sightings / Chuck berry and John lennon

« Last post by madaradio on August 21, 2020, 01:49:43 pm »

https://youtu.be/ZbGuxGGOIV0

The infamous yoko ono massacre. Bass player is playing a 2000s

3

Q & A / Re: Sun Solarus volume and eq

« Last post by DoomSunn on August 17, 2020, 04:42:39 pm »

Got it thanks!!

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Q & A / Re: Sun Solarus volume and eq

« Last post by EdBass on August 17, 2020, 07:44:40 am »

Not sure where on the planet you live, so...
In US currency, a "dime" is 1/10 of a dollar.

In most guitars cultures the term "dimed" is slang for volume knob on 10, and often used for having ALL the knobs set to 10. Wide open, no attenuation.

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Q & A / Re: Sun Solarus volume and eq

« Last post by DoomSunn on August 16, 2020, 01:49:12 pm »

By master volume I was meaning volume. I only
have the one knob on the left.
What your describing sounds on par with mine. The bass definitely can go it oblivion when pushed.
What do you mean by dimmed?
? ?I've dimed a few of them just to see what happens??

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Q & A / Re: Sun Solarus volume and eq

« Last post by EdBass on August 16, 2020, 11:39:29 am »

If your amp has a master volume, it's been modified. The response may not be "normal", depending on what's been done.

My stock Sunns extend deeper into the low end when I turn them up. The bass boost switches on my 200Ss and 2000Ss sound great at low volume, but make the amps saturate into useless mud at normal gig volumes. I don't get to "10" though, tonally there's really nothing up there I'm interested in.

I've dimed a few of them just to see what happens, but primarily I'm looking for tight and clean, with a little bit of snarl when I dig in.

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Q & A / Sun Solarus volume and eq

« Last post by DoomSunn on August 15, 2020, 08:19:34 pm »

I have noticed that when I am turning up the master volume on the amp that it sounds like
the signal is getting eq’d at different volume settings. For example at 10 it sounds bassier and at 1 or two it almost sounds high passed.

I am new to Sunn amps and tube amps in general, just wondering if this kind of behavior is normal?

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DIY / Re: Sentura II Restoration - Tremolo Bug/Roach Replacement Photocell

« Last post by Watson on August 08, 2020, 03:11:46 pm »

There are a multiple versions of these early SUNN amp schematics.  I was just interested in the output section for drawing the mod I want to make for the dual bias pots.  The one you posted is a later circuit design and probably more accurate.  The one I used for the output section showed 6550 tubes rather than KT88 so it is an older schematic and also listed 100S, Sceptre and Solarus although the output section doesn't differ. 

I went through service bulletins I have and here is what I think is some more good information on the vibrato related components. These are Fender service bulletins but the information is also applicable as SUNN used similar or the same technology for the photo-optic bug/roach as I was told by Conrad.

I hope these are helpful for anyone interested in the tremolo circuit (actually a vibrato circuit).  FWIW, a Tremolo modulates volume (like turning the volume control up and down quickly) whereas Vibrato shifts the frequency of the notes being played (like bending a string) so despite being labeled Tremolo on the amp's face plate, it is really a Vibrato circuit.

Service Bulletin 5 (Tech Notes-Defective_Photocells.pdf) addresses Vibrato failures and among other things mentions that the Vibrato bug assembly consists of and LDR and a NE2 Neon lamp.   

Service Bulletin 9 (Tech Notes-Vibrato_Ticking_Fix.pdf) addresses Vibrato ticking and corrective action.

Service Bulletin ? (Tech Notes-Tube_Amp_Topics.pdf) is a general review document of many tube amp issues discussed in previous Service Bulletins. Page 3 contains more information on the Vibrato LDR/Lamp bug and also a little bit on the design of the phase shift oscillator used in the design.  Again, the same basic design used by SUNN with the triple pot circuit.

9

DIY / Re: Sentura II Restoration - Tremolo Bug/Roach Replacement Photocell

« Last post by patlaw on August 08, 2020, 10:56:36 am »

The wiring for the input circuit and photocell are different from the schematic I have. Is that intentional?

10

DIY / Re: Sentura II Restoration - Tremolo Bug/Roach Replacement Photocell

« Last post by Watson on August 08, 2020, 01:48:15 am »

Just Photoshop.